1. Field of the Invention
The present invention relates to injection molding machines and, more particularly, to a plastics injection molding machine which has a die closing unit mounted on a pivot frame, for the selective horizontal or vertical orientation of the die closing unit on the machine base of the injection molding machine.
2. Description of the Prior Art
In the majority of injection molding machines, the die closing unit is oriented horizontally, meaning that the die opening and die closing movements take place along a horizontal axis. For the axial injection of plastic raw material into the injection molding die, the injection unit is located conveniently on top of the machine base, immediately behind the stationary die carrier plate, or behind the stationary cylinder assembly, in the case of a pull-type die closing unit. For radial injection, i.e. injection in the parting plane of the injection molding die, it is necessary for the injection unit to be mounted either on top of the stationary die carrier plate or on the horizontal tie rods, in a vertical orientation.
For certain production situations, it has been found to be preferable to obtain a radial injection configuration by moving the die closing unit into a vertical orientation, so that the injection unit can be mounted horizontally on top of the machine base, in essentially the same arrangement which is used for the axial injection with a horizontally oriented die closing unit. However, the lack of vertical adjustability of the injection unit on the machine base makes it necessary for the vertically oriented die closing unit to be adjustable axially--i.e. vertically--in relation to the machine base, in order to achieve alignmen,t between the injection nozzle of the injection unit and the parting plane of the injection molding die.
For a selective horizontal and vertical orientability of the die closing unit, it is therefore necessary to arrange the die closing unit on a horizontal pivot axis near the forward upper extremity of the machine base and, further, to make the die closing unit axially adjustable in relation to this pivot axis.
The prior art in this field includes U.S. Pat. No. 3,086,244 which discloses an injection molding machine which utilized the tie rods of the die closing unit to serve both as stationary guides for the movable die carrier plate and as supporting members for the entire die closing unit. For this purpose, the two tie rods engage clamping bores of two pivotable bearing supports. The axial adjustability of the die closing unit is obtained by shifting the tie rods in these clamping bores. But, because the tie rods are subject to deflection under the weight of the die closing unit, this configuration is suitable only for an injection molding machine with a short and lightweight die closing unit.
Another injection molding machine with a pivotable die closing unit is disclosed in U.S. Pat. No. 3,751,203. In this case, the die closing unit is carried by a pivot frame which is pivotably connected to the upper extremity of the machine base by means of a transversely mounted pivot shaft. The axial adjustability of the die closing unit in relation to the pivot shaft is obtained by adjustably clamping the stationary cylinder mount of the die closing unit to the pivot frame, using sliding members which are clampable against matching profiles of the pivot frame.
A similar solution is proposed in U.S. Pat. No. 3,852,010 which discloses a configuration in which the pivot frame is an optional component, the horizontally oriented die closing unit being mountable either on top of the pivot frame or directly on top of the machine base.
All these prior art solutions have practical limitations, because of their lack of structural rigidity and/or their structural complexity, arising from the need for an axial adjustability of the vertically oriented die closing unit.